Print head having cup shaped protective member



Dec. 13, 1966 J. F. MlLNE ET AL 3,291,276

PRINT HEAD HAVING CUP SHAPED PROTECTIVE MEMBER Filed April 30, 1965 2Sheets$heet 1 PRINT HEAD HAVING CUP SHAPED PROTECTIVE MEMBER Filed April30, 1965 Dec. 13, 1966 J. F. MILNE ETAL 2 Sheets-Sheet 2 mommmuomm 20mmOEMEDZ Lo am- 16 XEFSE OZEOQMQ mad: MEG Qzooww 1 ow 56m 326m Fzm2m omum/E 23m 397E182 l United States Patent Ofiice 3,291,276 PRINT HEADHAVING CUP SHAPED PROTECTIVE MEMBER James F. Milne, Penfield, N.Y., andPhilip E. Norgren,

Stamford, Conrn, assignors to Sperry Rand Corporation, New York, N.Y., acorporation of Delaware Filed Apr. 30, 1965, Ser. No. 452,215 11 Claims.(Cl. 1971) The invention relates in general to printing apparatus andmore particularly to an improvement in apparatus for printing dataelectrically on electrosensitive record material.

Certain known printing arrangements provide a plurality of styli in apatterned arrangement'capble of producing characters through selectivetime energization of the styli as the printer is swept across the faceof the record material. The styli are physically separated andelectrically isolated from each other in a pattern most conducive to thegeneration of the desired characters.

In such systems the styli rest directly upon the record material andcurrent is caused to pass from the selected styli through the recordmaterial to a ground plate located at the opposite side of the recordmaterial, or from one styli through the paper to another styli. Thecurrent in passing through the record material causes distinct marks ordots which can be combined through proper timed energization of thestyli to form the data to be printed. Such a printing arrangement isdisclosed in applicants co-pending application Serial No. 356,527 filedApril 1, 1964.

One serious problem encountered with printing arrangernents of the typementioned above is a fouling of the printing head with dust particlesand other foreign matter due in part to the direct contact by the styliwith the recording materials and the effect of the electrostatic fieldgenerated by these styli. As a result of this continued depositing ofdust particles and other foreign matter on the styli and other elementsof the print head, a deterioration of the printing quality and eventualfailure to print results from continued use of such devices. Whilemechanical means for physically cleaning the print head during eachcycle of scan have been suggested, such solutions are cumbersome,expensive and have proven to be ineflicient and impractical.

It is therefore an object of the present invention to provide animproved arrangement for forming characters from a styli printer whereinmeans are provided to prevent the accumulation of foreign matter on theindividual styli during the print operation.

It is a further object of the instant invention to provide such aprinter wherein the means for preventing the accumulation of foreignmatter on the print head is simple, inexpensive and highly reliable.

It is still another object of the present invention to provide such aprinter wherein the means for preventing the accumulation of foreignmatter on the printing head additionally increases the stability of thestyli to improve print clarity and reduce the scratching of therecording medium.

According to a preferred embodiment of the invention, sixteen individualstyli, each in the form of a pin, are mounted in a printing head,adapted to reciprocate across the recording material with the styli incontact therewith. The pin-type styli are each electrically insulatedfrom one another and spaced apart into a matrix configurated generallylike the digit 8. Each stylus is 3,291,276 Patented Dec. 13, 1966yieldably mounted in the print head, protrudes therefrom and is biasedby a spring into contact with the record material.

A cap made from a phenolic or sirnlar material and a gasket are mountedover the end of the print head from which the syli project. The gasketis made from a thermoplastic resin, preferably a plastic of thepolytetrafluoro-et'hylene type of fluorocarbon. The latter substance iscommonly known and sold under the trademark Teflon. The properties ofTeflon, which include resistance to high and low temperatures, excellentdielectric properties, high impact strength and low 00- efficient offriction, are well known. This combination of cap and gasket is springloaded to the print head so that the Teflon gasket during the printoperation rides across the face of the recording material. The styliproject through the cap and through the Teflon gasket to contact theface of the recording material; however, due to the spring bias on thecap and gasket combination only the cross-sectional ends of the styliare exposed and these are pressed directly onto the record material.

As a result of the Teflon gasket, a seal is provided around the printpins or styli without, however, preventing independent print pinmovement. Each stylus therefore remains individually yieldable so as topermit automatic individual adjustment thereof in response to unevennessof record material and uneven wear of the individual styli; however, forall practical purposes, each stylus is completely sealed except for itsextreme tip end.

The Teflon has very low coeflicient of friction, and a high dielectricstrength and the phenolic cap provides a rigid backing to keep theTeflon gasket from distorting. As a result of this effective isolationand support of the individual styli, fouling of the print head iseliminated, insuring good printing qualities of the device over aprolonged period of operation.

In addition, the provision of the additional gasket and cap about theprinting head provides increased support of the styli alongsubstantially their entire length to the very end thereof in contactwith the record paper. This added support of the styli materiallyincreases the stability thereof, improving the print clarity andreducing scratching marks on the paper, noted in connection with priorart arrangements.

The many objects and advantages of the instant invention can be seenfrom the above discussion, and will be further clarified by thefollowing description when taken in conjunction with the accompanyingdrawings wherein:

FIGURE 1 is a simplified schematic view in perspective of portions of aprinter in accordance with the invention;

FIGURE 2 is a simplified schematic view greatly enlarged of the printinghead of FIGURE 1, showing the configuration of the styli matrix;

FIGURE 3 is a schematic, cross-sectional view in side elevation andgreatly enlarged of a pair of pin styli taken through the printing headof FIGURE 1 and including the improvement of the instant invention, and

FIGURE 4 is a perspective view of the print head partly in section;

FIGURE 5 is a simplified schematic block diagram of the energizingcircuits for the printing head of FIGURE 1.

Referring to FIGURE 1, printing is accomplished on a tape or strip 330of chemically treated paper of the electrosensitive type. A tapeconveyor of any conventi-onal design is represented schematically bymerely a conveyor roller 332; it being understood that the tape conveyoris adapted to move tape 330 line by line to place successive lines ofthe tape into printing position; the direction of tape movement beingindicated by the directional arrow shown on roller 332.

A stylus or printing head 334 is slidably mounted on a guide rod 336 formovement transversely of tape 330 at the printing position. Printinghead 334 may be driven by any suitable means from the left edge of tape330, the initial printing position, to the right edge of the tape duringthe printing cycle, and then back to the left tape edge, in preparationfor printing the next line. Such driven movement is preferably effectedat a substantially constant speed by printing head conveying mechanism(not shown) which transmits driven motion to printing head 334 by meansof a timing belt 338 attached by fasteners 340 to a printing head 334.It is to be understood that incident to printing head 334 being returnedto its initial printing position at the end of a printing cycle, roller332 of the tape conveyor (not shown) moves tape 330 in the direction ofthe directional arrow to place the next printing line of tape 330 intoprinting position. Actuation of roller 332 is effected by theabove-mentioned printing head conveying mechanism.

Printing head 334 is formed of an electrically nonconductive mate-rialand is provided in the illustrated embodiment with sixteen individualstyli assemblies 342 (FIGURE 3), each having a stylus or electrode inthe form of a rod-like pin 344. The pins are designated P1 through P16(FIGURE 2) to differentiate the pins from one another. Styli pins 344(FIGURE 3) protrude from the bottom of printing head 334, fourteen ofwhich pins (Pl-P14) are arranged into a matrix having the configurationof a digit 8 slightly slanted to the left, as seen in the bottom View ofthe printing head 334, shown in FIGURE 2. In addition, a pair of pins,P15 and P16, are provided for inserting the decimal point designation inthe proper position between numerals along the line of print.

The pin 344 of each styli assembly 342 is formed of conductive material,preferably of tungsten and is slidably disposed in an associated pinhole or channel 348 defined in a bottom portion 352 of printing head334. Each pin 344 is provided with a sleeve 354 of conductive material,such as stainless steel, which sleeve is press fit onto the upper end ofthe pin. Sleeve 354 is slidably confined in a channel 356 aligned withchannel 348 and defined in an intermediate portion 358 of printing head334 to permit up and down movement of pin 334 and sleeve 354 in channel356. A biasing spring 362 of the coil type and of conductive material isprovided for each pin 44 and is loosely disposed under compression inthe channel 356 provided for its associated pin. Spring 362 pressesagainst sleeve 354 of its associated pin 344, biasing the pin downwardto maintain the free or lower end of the pin in constant contact withthe upper surface of tape 330. Downward movement of pin 344 is limitedby its sleeve 354 abutting a shoulder 364 formed by printing headportion 352 where channel 348 joins channel 356.

An electrical connecting lead 366 is provided for each pin 344 andextends through a hole 368 defined in a portion 370 of printing head334. Each lead 366 enters the channel 356 of its respective pin 344 andis connected electrically to the uppermost portion of the spring 362 insuch channel. The leads 366 serve to connect their respective pins 344(Pl-P16) to the pin energizing circuits.

It may be noted that with the described mounting arrangement of eachstyli assembly 342, each styli pin 344 is individually spring biased tocontinually bear upon and frictionally engage the top surface of tape339, as printing head 334 is driven transversely of the tape. Suchindividual spring biasing automatically compensates for unevenness ofthe tape surface and for variation in the wear rates of the individualstyli pins 344. However, this direct contact of the styli pins with thepaper surface has a tendency, should the styli pins be exposed from theprint head, to pick up fibers from the paper, dust particles and otherforeign matter which shortly will cause a fouling of the print headconsiderably reducing, if not altogether disrupting, the printcapability of the arrangement.

As a result of the difficulties with fouling of the print headexperience-d by prior art devices, the instant invention proposes theinclusion of a boot 350 (FIGURE 4) over the print head, which bootconsists of a phenolic cap 351 and a Teflon gasket 353. The boot 350 isprovided with a plurality of holes, each in substantial alignment withone of the styli pins of the printing head so that the individuallyspring biased styli pins may protrude through the boot and contact therecording surface 330. The boot 350 is spring loaded with respect to theprint head by springs 380 recessed in channels or grooves 381 in the cap351. The springs 380 act upon pins 382 in contact with the collar 384surrounding the print head. The bias provided by springs 380 forces theTeflon gasket 353 against the surface of the tape 330 so that the stylipins 344 are completely isolated except for the crosssectional endswhich contact the surface of the tape. Since the Teflon gasket is inpressure contact with the tape 330 when the print head assembly is inthe print position, the end of the cap and Teflon gasket have a radiuscomparable to that of the roller 332 so as to insure good contactbetween the gasket and the paper over the full gasket area. The holes inthe cap 350 through which the print pins pass have a dimension onlyslightly larger than the pins themselves; however, due to the naturallubrication provided by the Teflon material, the pins may very easilyslide in and out of the print head in response to pressure by thesprings 362 insuring good contact between the pins 344 and the surfaceof tape 330. While the boot 350 is shown as being formed of two separateelements 351 and 353, it is within the purview of the invention toprovide the entire boot of a single material such as a fluorocarbonresin with a fi-ller so as to combine the low friction and highdielectric properties of Teflon with low wear and rigidity. In addition,the gasket 353 may be made from other materials having propertiessimilar to Teflon.

When the print head is released to the print position. the outer surface355 of bottom portion 352 (FIGURE 3) is stopped before engaging insidesurface 356 of the cap 351 by a stop 385 (FIGURE 4) on the capcooperating with suitable means (not shown) so that a gap 357 isprovided therebetween. The individually bias-ed styli pins 344 protrudeslidably through the boot 350 to engage the record surface 330. Thespring bias on the boot relative to the print head places the frontsurface of the Teflon gasket 353 firmly but resiliently against therecord surface to be printed upon. Thus, the styli pins 344 arecomplete-1y surrounded by the boot 350 so that only the cross-sectionalend surfaces of the pins are exposed and these firmly contact thesurface of tape 330. In this position, the record sheet engaging ends ofthe pins are substantially in the same plane as the outer surface of theTeflon gasket 353.

With such an arrangement, the gasket 353 which follows the record sheetcurvature is maintained firmly against the record surface as it and theprint head are driven transversely of the record sheet. The Teflon sheetbiased against the record surface eliminates the gap which washeretofore present between the print head and the record sheet and inwhich dust particles accumulated, fouling the pins. In addition to theelimination of such gap, and the relatively tight fit of the pins asthey pass through the Teflon gasket, the gasket effectively mashes theexploded dust particles of the record sheet surface back into the sheetsurface such that no noticeable loose dust particles are formed to foulthe pins. This wiping action of the Teflon gasket as it moves across therecord 5 surface under pressure forcing the dust particles back into thesurface impregnates the surface with all looseparticles preventing theseparticles from entering the pin channels in the print head and fromgenerally fouling the styli or other portions of the printingarrangement.

In addition to solving the fouling problem, as indicated above, theprovision of the boot 350 over the print head provides an added supportfor the styli pins over substantially their entire length to the veryends which contact the record surface 330 resulting in increasedstability and more accurate registration of the pins so that greaterclarity in printing is achieved and scratching of the surface due tovibrations in the pins is completely eliminated.

By selectively electrically pulsing certain combinations of pins 344 ofthe styli matrix of FIG. 2, the configurations of numerals through 9 andsome special symbols may be printed upon tape 330 (FIG. 1), as printinghead 334- is moved transversely thereto. Such marking is effected in thepreferred embodiment by causing a succession of current pulses to flowfrom one pin 344 (FIG. 3) along the chemically coated surface ofconductive tape 330 to a second pin 344 which is associated with andspaced from the first pin. For example, with the pair of pins (e.g., P1,P2) shown in FIG. 3, a pulse of current may be caused to flowsuccessively from P1 along tape 330 to pin P2. Such current flow causeschemically treated tape 33b to darken or change color at the two pointswhere pins P1 and P2 engage the tape surface to provide legible distinctmarks thereat, which due to suecessive pulsation thereof may take theform of elongated dots or lines. The electrical pulsing of the pins issubstantially instantaneous, such that movement of printing head 334relative to tape 33% is effectively stopped during printing. Thisprevents blurring, notwithstanding the relative motion between pin 344and tape 330 during the printing.

The sixteen styli pins 344 (Pl-P16, FIG. 2), comprising the digit 8styli matrix and a decimal point designation as mentioned above, areelectrically connected to the pin energizing circuits in pairs.

The pin styli 344 are therefore divided into pin pairs and an electricalstyli energizing circuit is provided for each pair of pins (FIGURE Thus,eight pin energizing circuits, or driving circuits 371-378 are utilizedfor energizing the sixteen pins. The digits 0 and 1 through 9, pluscertain symbols, such as the letter C and the decimal point may beprinted by causing the driving circuits to successively energizeselective pin pair combinations in accordance with a particular timesequence.

The driving circuits utilize means in the form of a decoding matrix 383for detecting the input of certain pin selection signals derived from aninput processor. The decoding matrix translates the selection signalsand conditions the driving circuits to effect subsequent energization ofassociated pin pairs or to prevent such energization, as the signalsdictate. The detecting means also automatically and continually respondsto changes in pin selection as denoted by the selection signals.

A print signal causes energization of print initiating means (not shown)which generate initiating or gating signals which are appliedsimultaneously to all driving circuits via the decoding matrix 383. Thiscauses the driving circuits of the selected pin pair combination to besimultaneously energized to form the desired character on the recordmedium, while those of the unselected pin pairs are maintainedunenergized in accordance with the preconditioned state of the drivingcircuits. The print initiating signals are in the form of electricalpulses.

During printing, the printing head 334 is moved at a substantiallyconstant speed transversely of the record tape 330. Selection of the pinpairs to be energized and pulsing of their respective driving circuitsare synchronized with transverse movement of the print head such thatdesired characters are printed sequentially on a print line. In thisway, energization of selection pin pairs in response to the common printinitiating pulses will be sufficiently instantaneous so as to appear tostop relative motion between the print head and record material,producing distinct printed characters on the record material,notwithstanding such relative motion.

Such an arrangement obviates the need to use a ground" plate, as inprior art system, and minimizes the amount of equipment required forproper operation. The simultaneous energizat-ion of selected pin pairsby the common print initiating signals to print a character on therecord medium also provides a highly reliable printing arrangement atminimal cost.

It is, of course, understood that the above-described arrangement forprint head energizia'tion is presented only as an example of onepossible arrangement for performing the required function, and anysimilar known arrangement or system for energization of stylus printingapparatus could be used with the disclosed print head construction.

As changes can be made in the above-described construction and manyapparently different embodiments of this invention can be made withoutdeparting from the scope thereof, it is intended that all mattercontained in the above description or shown on the accompanying drawingsbe interpreted as illustrated only and not in a limiting sense.

What is claimed is:

1. In stylus printing apparatus for electrically printing on chemicallytreated record material in the form of a tape which is movablelongtiudinally past a printing station, a printing head having aplurality of styli electrodes in continuous contact with one surface ofsaid tape, said styli electrodes being electrically insulated one fromthe other, means for moving said printing head in transverse excursionswith respect to said tape at said printing station, electric circuitmeans energizable for selectively causing pulses of current to flowsimultaneously from a predetermined combination of said styli electrodesthrough said tape to produce distinct marks on said record surface, andelectrode shielding means surrounding said print head and having aplurality of apertures in alignment with said styli electrodes, throughwhich said electrodes protrude, said electrode shielding means having anouter surface portion in contact with said one surface of said tape, andadapted for slidable engagement therewith during said excursions.

2, An apparatus for printing electrically on electrosensitive recordmaterial in the form of a tape which is movable longitudinally past aprinting station, a printing head having a plurality of styli electrodesprotruding from one end thereof, each of which is electrically insulatedone from the other and spaced apart into a styli matrix of predeterminedconfiguration, means for moving said printing head transversely of saidtape at said printing station and maintaining a free end portion of eachof said styli electrodes in contact with one surface of said tape,electrode energizing means energizable for applying electrical energysimultaneously to selected ones of said styli electrodes to causecurrent to pass through said selected electrodes through said tape, andelectrode shielding means positioned over said one end of said printinghead for encasing all of each of said styli electrodes except for thecross-sectional surfaces at said free ends thereof.

3. In printing apparatus as set forth in claim 2 wherein said electrodeshielding means is formed of electrically non-conducting material andhas for each of said electrodes a receiving aperture defined therein,and each of said electrodes is slidably mounted in its associated one ofsaid apertures and is provided with means for biasing saidcross-sectional end of its associated electrode into engagement withsaid tape.

4. In apparatus for printing electrically on electrosensitive recordmaterial, the combination of a printing head having at least two stylielectrodes with substantially coplanar end surfaces, said lectrodesbeing electrically insulated and spaced apart from each other, means formounting said printing head and adapted to maintain said stylielectrodes in a predetermined configuration and in engagement with saidrecord material, and electrodes shielding means slidably positioned oversaid printing head and substantially enclosing said styli electrodes,said shielding means including an end portion adapted to accommodatesaid electrodes in engagement with said record material, said endportion having an outer surface substantially coplanar with saidcoplanar end surfaces and engaging said record material.

5. In a stylus printing apparatus for electrically printing onchemically treated record material in the form of a tape which ismovable longitudinally past a printing station, a printing head havingat least two styli electrodes protruding from one end thereof intocontinuous contact with a surface of said tape at said printing station,said stylus head being movable transversely of said tape for printingalong a transverse line on such tape, electric circuit means energizablefor causing pulse of current to flow from a first one of said stylielectrodes to the other of said electrodes through said tape producingdistinct marks on said tape surface where said electrodes contact saidtape surface, insulating cup means positioned over said one end of saidprinting head with said electrodes protruding through the bottomthereof, the outer surface of the bottom of said cup means beingprovided with a thermoplastic resin layer, said layer being providedwith apertures in alignment with said electrodes, and biasing means forsaid cup means normally urging said outer surface of the bottom thereofinto contact with said tape, such that the tape contacting portion ofsaid electrodes and said outer surface are coextensive.

6. A printing head for stylus printing apparatus capable of printing onchemically treated record material comprising an insulating block, aplurality of parallel spaced electrodes protruding from one end of saidblock, means for effecting individual electrical connections to saidelectrodes through said block, and electrode shielding means positionedover said one end of said block and substantially enclosing saidelectrodes, said shielding means being movable with respect to saidblock and said electrodes and including biasing means for normallybiasing said shelding means outwardly from said block in the directionof extension of said electrodes.

7. A printing head as set forth in claim 6 wherein said shielding meansis cup-shaped and provided with a plurality of apertures in substantialalignment with said electrodes for accommodating the passagetherethrough of said electrodes,

said shielding means has a curved surface including said apertures forconforming to the surface of said record material, and

said electrodes are spring biased within said insulating block for axialmovement relative to said block and said shielding means.

8. A printing head for stylus printing apparatus capable of printing onchemically treated record material comprising an insulating block, aplurality of parallel spaced electrodes protruding from one end of saidblock, means for effecting individual electrical connections to saidelectrodes through said block, and electrode shielding means positionedover said one end of said block and substantially enclosing saidelectrodes, said shielding means being movable with respect to saidblock and said electrodes and including biasing means for normallybiasing said shelding means outwardly from said block in the directionof extension of said electrodes,

said shielding means being cup-shaped and being provided with aplurality of apertures in substantial alignment with said electrodes andaccommodating the passage therethrough of said electrodes,

said shielding means having a curved surface including said aperturesfor conforming to the surface of of said record material,

said curved surface of said shielding means being formed of a materialhaving low friction and high dielectric properties as compared to saidelectrodes.

9. A printing head for stylus printing apparatus capable of printing onchemically treated record material comprising an insulating block, aplurality of parallel spaced electrodes protruding from one end of saidblock, means for effecting individual electrical connections to saidelectrodes through said block, and electrode shielding means positionedover said one end of said block and substantially enclosing saidelectrodes, said shielding means being movable with respect to saidblock and said electrodes and including biasing means for normallybiasing said shielding means outwardly from said block in the directionof extension of said electrodes,

said shielding means being cup-shaped and being provided with aplurality of apertures in substantial alignment with said electrodes andaccommodating the passage therethrough of said electrodes,

said shielding means having a curved surface including said aperturesfor conforming to the surface of said record material,

said shielding means being formed of a rigid insulating cup and a curvedouter layer of thermoplastic resin.

10. A printing head for stylus printing apparatus capable of printing onchemically treated record material comprosing an insulating block, aplurality of parallel spaced electrodes protruding from one end of saidblock, means for effecting individual electrical connection to saidelectrodes through said block, and electrode shielding means positionedover said one end of said block and substantially enclosing saidelectrodes, said shielding means being movable with respect to saidblock and said electrodes and including biasing means for normallybiasing said shielding means outwardly from said block in the directionof extension of said electrodes,

said shielding means being cup-shaped with a continuous sidewall portionextending from an end portion, and being provided with a plurality ofapertures in substantial alignment with said electrodes andaccommodating the passage therethrough of said electrodes,

said apertures in said shielding means extending through said endportion and having a diameter substantially equal to the diameter ofsaid electrodes.

11. A printing head for stylus printing apparatus capable of printing onchemically treated record material comprising an insulating block, aplurality of parallel spaced electrodes protruding from one end of saidblock, means for effecting individual electrical connections to saidelectrodes through said block, and electrode shielding means positionedover said one end of said block and substantially enclosing saidelectrodes, said shielding means being movable with respect to saidblock and said electrodes and including biasing means for normallybiasing said shielding means outwardly from said block in the directionof extension of said electrodes,

said shielding means being cup-shaped with a continuous sidewall portionextending from an end portion, and being provided with a plurality ofapertures in substantial alignment with said electrodes andaccommodating the passage therethrough of said electrodes,

said electrodes being spring biased within said insulating block foraxial movement relative to said block and said shielding means,

said apertures in said shielding means extending through said endportion and having a diameter substantially equal to the diameter ofsaid electrodes.

References Cited by the Examiner UNITED STATES PATENTS Howell 346-139Mathes 346-139 5 Finch 346-139 Faus 346-74 Williamson 346-74 Clurmah eta1. 346-139 X Willard 346-74 10 Epstein et a1. 346-74 Metzer 346-74Christopherson 178-30 X Epstein et a1. 178-30 X Lynott 346-139 XProudfit 346-74 Schroder et a1 147-1 X ROBERT E. PULFREY, PrimaryExaminer.

DAVID KLEIN, Examiner.

E. S. BURR, Assistant Examiner.

1. IN STYLUS PRINTING APPARATUS FOR ELECTRICALLY PRINTING ON CHEMICALLYTREATED RECORD MATERIAL IN THE FORM OF A TAPE WHICH IS MOVABLELONGITUDINALLY PAST A PRINTING STATION, A PRINTING HEAD HAVING APLURALITY OF STYLI ELECTRODES IN CONTINUOUS CONTACT WITH ONE SURFACE OFSAID TAPE, SAID STYLI ELECTRODES BEING ELECTRICALLY INSULATED ONE FROMTHE OTHER, MEANS FOR MOVING SAID PRINTING HEAD IN TRANSVERSE EXCURSIONSWITH RESPECT TO SAID TAPE AT SAID PRINTING STATION, ELECTRIC CIRCUITMEANS ENERGIZALE FOR SELECTIVELY CAUSING PULSES OF CURRENT TO FLOWSIMULTANEOUSLY FROM A PREDETERMINED COMBINATION OF SAID STYLI ELECTRODESTHROUGH SAID TAPE TO PRODUCE DISTINCT MARKS ON SAID RECORD SURFACE, ANDELECTRODE SHIELDING MEANS SURROUNDING SAID PRINT HEAD AND HAVING APLURALITY OF APERTURES IN ALIGNMENT WITH SAID STYLI ELECTRODES, THROUGHWHICH SAID ELECTRODES PROTRUDE, SAID ELECTRODE SHIELDING MEANS HAVING ANOUTER SURFACE PORTION IN CONTACT WITH SAID ONE SURFACE OF SAID TAPE, ANDADAPTED FOR SLIDABLE ENGAGEMENT THEREWITH DURING SAID EXCURSIONS.